1. Field of the Invention
The present invention relates to an integrated circuit package.
2. Description of Related Art
Integrated circuits are typically housed within a plastic package commonly referred to as a quad flat pack (QFP). Flat packs contain a lead frame which has a plurality leads that are connected to an integrated circuit die. The die is encapsulated by a hard plastic housing which mechanically supports and electrically insulates the integrated circuit. The leads are typically soldered to a printed circuit board.
The package is assembled by placing the die and lead frame into a mold and then injecting a plastic encapsulant into the mold cavity. The encapsulant is typically injected through a single gate located at one corner of the mold cavity. Encapsulant flows through the gate, into the mold cavity and across one side of the lead frame. The injected plastic also flows through the spaces between the leads of the lead frame and across the opposite side of the integrated circuit to totally encapsulate the IC die.
The pressure of the injected plastic must be high enough to push the encapsulant through the lead frame openings and fill the entire mold cavity. Relatively small lead frame spacing creates corresponding thin openings between the leads. The smaller openings increase the fluid resistance of the encapsulant. Higher injection pressures must be supplied to overcome the increase in fluid resistance. It has been found that relatively high injection pressures may cause an undesirable deflection of the lead frame. It would therefore be desirable to have a method of injecting encapsulant into the mold of an integrated circuit package, which requires a lower injection pressure than methods in the prior art.